ADSORPTION DYNAMICS OFCO2ON HYDROGEN PRECOVEREDZn-ZnO(0001): A MOLECULAR BEAM STUDY

Abstract

Presented are initial, S0, and coverage, Θ, dependent, S(Θ), adsorption probability measurements, respectively, of CO2adsorption on a hydrogen precovered, polar, Zn -terminated surface of ZnO , parametric in the impact energy, Ei, and atomic hydrogen precoverage, ΘH. Furthermore, CO2Thermal Desorption Spectroscopy has been used to estimate ΘHas well as the binding energy of CO2on H / Zn - ZnO . The S(Θ) curves are below Ei=0.56 eV , consistent with precursor-mediated adsorption (S~ const ), and above that impact energy with adsorbate-assisted adsorption (S increases with Θ). Although a decrease in the CO2binding energy from 32.5 to 28.8 kJ/mol with ΘHis present, S(Θ, ΘH) curves are consistent with a physical site blocking, as demonstrated by Monte Carlo Simulations.